This invention relates in general to light-weight vehicle wheels, and in particular to a vehicle wheel including a one-piece backbone wheel cast from a light-weight metal and a styled plastic wheel face molded on the backbone wheel.
In the early 1970""s, Motor Wheel Corporation developed and introduced a composite metal-plastic styled wheel known as a xe2x80x9cPOLYCASTxe2x80x9d wheel. The POLYCAST wheel included a metal wheel of simple, conventional configuration as a basic structural component, and a permanently adhered ornamental plastic body covering portions of the wheel disc. The metal wheel portion of the POLYCAST wheel was formed from two pieces of stamped steel which were welded together.
Cast vehicle wheels formed from light-weight metals, such as aluminum, magnesium, titanium, and alloys thereof, have become increasingly popular. Such cast wheels provide both a reduction in weight from steel wheels and can be cast having an attractive styled appearance.
A conventional cast vehicle wheel presents disadvantages in terms of weight and cost of the wheel. Much of the metal used in the wheel disc of a conventional cast vehicle wheel is added for style alonexe2x80x94it is not needed for high stress areas or load carrying capabilities. For example, a conventional cast vehicle wheel has relatively wide spokes. The spokes must also be cast relatively thick to allow the molten metal to fill the entire mold during the casting process. Even though the cast vehicle wheel is made from a light-weight metal, the greater amount of metal used increases the weight and cost of the cast wheel.
The POLYCAST wheel also had some disadvantages. Because the metal wheel portion of the POLYCAST wheel was made from two pieces of steel which were welded together, the costs of production and tooling were higher than the costs for making a one-piece wheel. The stamping process used to make the metal wheel portion was very limited in its ability to produce a wheel disc that was varied in thickness in different portions of the disc. Consequently, the stamped wheel disc was relatively thick throughout the entire area of the disc. The use of steel instead of a light-weight metal in the metal wheel portion of the POLYCAST wheel, and the relatively thick wheel disc, created a relatively heavy wheel.
The ornamental plastic body of the POLYCAST wheel did not cover a steel flange on the outboard end of the wheel rim, around the perimeter of the wheel disc. The plastic body covering most of the wheel disc was finished with a chrome plating, while the steel flange was usually finished with a silver paint, because steel is more difficult to chrome plate than plastic. The difference between the silver paint on the flange and the chrome plating on the wheel disc could be easily observed, which detracted from the appearance of the wheel.
The present invention provides a light-weight vehicle wheel which overcomes the drawbacks associated with conventional cast vehicle wheels and with the POLYCAST wheel. The vehicle wheel includes a one-piece backbone wheel cast from a light-weight metal. The backbone wheel comprises a generally cylindrical wheel rim adapted to carry a vehicle tire, and a wheel disc backbone extending across the wheel rim. The wheel disc backbone is adapted to be mounted on the vehicle. A styled plastic wheel face is molded on the wheel disc backbone.
In another embodiment of the invention, the styled plastic wheel face is molded on the wheel disc backbone and the outboard end of the wheel rim. The plastic wheel face forms a plastic flange on the outboard end of the wheel rim.
In a further embodiment, the wheel disc backbone comprises a wheel hub adapted to be mounted on the vehicle and a plurality of backbone spokes extending between the wheel hub and the wheel rim. The backbone spokes have a thickness of not greater than about 1.5 inches.
The invention also contemplates a method of producing a vehicle wheel. The method includes the steps of: (a) casting a one-piece backbone wheel from a light-weight metal, the backbone wheel comprising a generally cylindrical wheel rim adapted to carry a vehicle tire, and a wheel disc backbone extending across the wheel rim, the wheel disc backbone adapted to be mounted on the vehicle; and (b) molding a styled plastic wheel face on the wheel disc backbone.
In contrast to the wheel portion of the POLYCAST wheel, which was made by a stamping process, the backbone wheel of the present invention is made by a casting process. The casting process allows the thickness of different portions of the wheel disc backbone to be varied, so that the wheel disc backbone can be formed from the minimum amount of metal needed to withstand loads and stresses on the wheel disc. Reducing the amount of metal provides significant savings in weight and cost of the wheel. The weight of the wheel is further reduced compared to the POLYCAST wheel by making the backbone wheel from a light-weight metal instead of from steel. In contrast to the two-piece welded wheel portion of the POLYCAST wheel, the one-piece cast backbone wheel of the present invention lowers tooling costs, lowers production costs, and provides more flexible production.
Unlike a conventional cast vehicle wheel in which much of the metal used in the wheel disc is added for style alone, the backbone wheel of the present invention can use the minimum amount of metal in the wheel disc backbone needed to withstand loads and stresses on the wheel disc. The styled plastic wheel face provides styling for the wheel disc. Consequently, the vehicle wheel of the present invention can be constructed with a smaller amount of metal than a conventional cast vehicle wheel, thereby reducing the weight and cost of the wheel. With a lighter wheel, a vehicle accelerates faster and/or with less gas consumption. The suspension system adapts to irregularities in the road surface better. Lighter springs and shock absorbers can be used on the vehicle. The styled plastic wheel face can be molded for less cost than a metal wheel face, because the mold produces a more net shape in plastic which requires less secondary work. The plastic wheel face can also be chrome-plated or painted at a lower cost than metal because of the smoother surface finish produced. The molding of plastic instead of metal results in longer mold life and lower tool maintenance cost. In the preferred embodiment, the plastic wheel face extends over the outboard surface of the wheel flange on the outboard end of the wheel. This eliminates the need to apply a surface finish to two different materials.
Various other advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiments, when read in light of the accompanying drawings.